The present invention relates to an image reading device capable of reading images of documents being fed one by one and an image of a document placed on a document platen, as well as an image forming apparatus provided with such an image reading device.
One conventional image forming apparatus 130 as illustrated in FIG. 9 includes an image reading unit 20 having a top surface provided with a document platen 21 for placing a document thereon, and a document feeding unit 120 capable of covering and uncovering a top surface of the document platen 21. The image reading unit 20 includes first image reading means 23. The first image reading means 23 reads the image of a document placed on the document platen 21 positioned horizontally as a first document reading position R1 while moving parallel with the document platen 21. Alternatively, the first image reading means 23 reads the image of a document fed by the document feeding unit 120 by stopping the document at a second document reading position R2 which is different from the first image reading position R1. For this reason, the first and second image reading positions R1 and R2 lie in the same plane in the image reading unit 20.
The document feeding unit 120 defines therein a document feed path 101 for feeding documents one by one via the second document reading position R2. The document feeding unit 120 has a feed path (comprising the document feed path 101 and a branch path 102) extending from a document load tray 91 for accommodating therein documents to be read up to a document catch tray 93 for receiving documents finished with image reading via the second document reading position R2. The document load tray 91 and the document catch tray 93 are often disposed above the document platen 21 in such a manner that the trays 91 and 93 are positioned in tier to meet a request for space saving.
The feed path needs to pass the second reading position R2 which lies in the same plane as the document platen 21. The feed path is provided with a plurality of feed roller pairs each configured to feed a document by nipping it therebetween. At least a part of the feed roller pairs is located above the document platen 21. Therefore, the feed path includes a sloped portion (i.e., document feed path 101) which is inclined downwardly as it extends from the document load tray 91 located above the document platen 21 toward the second document reading position R2, and a curved portion (i.e., branch path 102) extending from the second document reading position R2 toward the document catch tray 93 located above the document platen 21. Small-sized documents, such as cards and business cards, are likely to cause feeding failures, such as damage to documents and paper jam, due to their deformation in the curved portion (i.e., branch path 102).
In order to reduce the number of occurrences of such feeding failures of small-sized documents, an image forming apparatus described in Japanese Patent Laid-Open Publication No. HEI6-115789 is provided with a document feed path 103 extending substantially horizontally from the downstream side of the second document reading position R2, in addition to the curved portion (i.e., document feed path 102), as shown in FIG. 9. In such an image forming apparatus 130, the document catch tray 92 is located downstream of the second document reading position R2 in the document feeding direction and positioned lower than the second document reading position R2, while a protruding portion 201 which accommodates therein feeding members, such as feed roller pairs located downstream of the second document reading position R2, protrudes downwardly from a bottom surface of the document feeding unit 120. On a top surface of the image reading unit 20, a dent portion 131 shaped to fit the protruding portion 201 of the document feeding unit 120 is formed near the document platen 21 to accommodate the protruding portion 201.
However, the dent portion 131 formed on the top surface of the image reading unit 20 at a location adjacent the document platen 21 raises the following problem. That is, in cases where only one page of a two-page spread of a book is to be read or in like cases, the document is sometimes placed in such manner that only part of the document (which is the part to be read) is positioned on the document platen 21 (i.e., first reading position R1) while the rest of the document (which does not need to be read) positioned to extend off the document platen 21 onto the dent portion 131, as shown in FIG. 10. In this case, a problem arises that the part of the document which extends off the document platen 21 onto the dent portion 131 is caught between the protruding portion 201 of the document feeding unit 120 in the closed position and the dent portion 131 to damage the document (see the point indicated by the non-relief arrow in FIG. 10).
A feature of the present invention is to provide an image reading device which is capable of making the feed path of the document feeding unit substantially straight without damage to a document placed to extend off the document platen 21, thereby suppressing the occurrence of the small-sized document feeding failure.